Air classifier



Feb. 16, A s BlNS v AIR CLASSIFIEZR Filed May 24. 1929 2 Sheets-Sheet 119 ATTORNEY Feb. 16, 1932. A. H. STEBBINS AIR CLASSIFIER Filed May 24,1929 2 Sheets-Sheet 2 ATTORNEY fier of Fig. 1;

Patented Feb. 16, 1932 UNITED STATES ALBERT H. STEBBINS, OF LOS ANGELES,CALIFORNIA AIR CLASSIFIEB Application filed May 24, 1929. Serial No.365,748.

This invention relates to air classifiers of the type in which rotativemovement is imparted to the material laden a1r to cause the heavierparticles to be thrown outwardly by centrifugal force.

One of the features of the present lnvention resides in the constructionwhereby a thin layer of air .and heavier material traveling adjacent thewall of the classifylng re-/ ceptacle are deflected out of thereceptacle, whereupon the heavier particles may be readily removed fromthe small volume of air in which they are suspended.

Another feature of the invention resldes in the construction whereby thematerials that settle out of the air within the classifying receptacleare divided into several grades by supporting a plurality of collectlnghoppers within the lower portion of the receptacle to catch thematerials that settle in d1fferent portions thereof.

Still another feature of the invention resides in the constructionwhereby the materials that settle out of the air adjacent the walls ofthe receptacle are directed across an apertured surface to subject thesematerials to an air sweeping operation. I

Other features of the invention and novel combination of parts inaddition to the above will be hereinafter described in connection withthe accompanying drawings which illustrate good practical forms of theinvention.

In the drawings Fig. 1 is a side elevation of an air classifierconstructed in accordance with the present invention;

Fig. 2 is a top plan view of the air classi- Fig. 3 is a sectional viewtaken on the line 3--3 of Fig. 1;

Fig. 4 is a vertical sectional view through the classifier taken on theline 44 of Fig. 2;

Fig. 5 is a sectional view taken on the line 5-5 of Fig. 1;

Fig. 6 is a sectional view taken on the line 6-6 of Fig. 1;

Fig. 7 on a reduced scale is a perspective view of a modified type ofair classifier; and Fig. 8 on an-enlarged scale is a sectional viewtaken on the line 8-8 of Fig. 3.

In the embodiment of the invention illustrated in the drawings thematerial laden air is delivered tangentially b a pipe 10 into areceptacle 11 to whirl in tlie receptacle about a vertical axis. The airthat enters the receptacle 11 through the pipe 10 may be drawn in fromthe atmosphere by suction means to be described, or this pine 10 maylead direct from a source of material laden air.

In the construction shown the receptacle 11 is provided at its upper endwith a dome 12. of reduced diameter for the purpose of efiecting furtherremoval of the heavier particles from this portion of the air classifierin a manner to bedescribed. It is not essential, however, that the dome12 have a diameter less than that of the receptacle 11.- Air isexhausted from the upper portion of the air classifier by a pipe 13which communicates with an opening formed in the dome cover 14 and thispipe 13, in the construction shown, leads to the suction side of a fan15-. '7 ,s'

The suction produced in the classifying receptacle by the exhaust pipe13 will serve to impart a rotative movement to the air drawntangentially into the receptacle through the inlet pipe 10 and this willserve to throw the heavier particles outward by centrifugal forceagainst the side walls of the receptacle so that, they will movedownwardly adjacent the side walls into a collecting hopper, to bedescribed. Since the air rotating near the central axis of theclassifier will have less velocity' than the air traveling near the sidewalls of the receptacle the materials settling out of the air near thecentral axis of the machine will be finer than those settling out of theair adjacent the side walls of the receptacle. ,It is desirable toprevent these finer particles from entering the collecting hopperprovided for the heavier particles, and this is accomplished inaccordance with the present invention by providing a plurality of nestedhoppers in the lower portion of the receptacle 11 and which serves tograde or classify the materials settling out of the air in thelowerportion of the receptacle. In the construction shown three of thesecollecting hoppers are provided and are indicated b 16, 17 and 18 andthe materials that enter t ese hoppers will pass downwardly into thedischarge pipes 19, 20 and 21. The heaviest particles which movedownwardly adjacent the side walls of the receptacle 11 in theconstruction shown will fall upon the inclined apertured surface 22which serves to direct these materials into the outermost collectinghopper 23 which directs these heaviermaterials into the discharge pipe24.

The object of providing the a-pertured surface 22 is to subject theseheavy particles to a final air treatment before they enter thecollecting hopper 23 and this is accomplished in the constructions shownin Figs. 1 to 6 inclusive by admittin air from the atmosphere to theunder ace of the apertured surface 22 so that it will be-drawn upwardlythrough these apertures into the' classifying receptacle 11 by theaction of the exhaustpipe 13. The air which passes upwardly through theapertures 25 of the plate 22 preferably serves also to promote thewhirling movement of the air within the receptacle 11. This isaccomplished by providing these apertures with inclined lips 25 adaptedto direct the jets of air entering these apertures so that they willimpart a whirling movement to the volume of air within the classifyingreceptacle. It willtherefore be seen that these air jets perform thedouble function of air-sweeping or cleansing the heavier particlesmoving across the inclined plate 22 to the mouth of the hopper 23 andalso of increasing the whirling movement of the air within theclassifying receptacle.

It is desirable to control the volume of air admitted from theatmosphere to the under face of the apertured surface 22. This isaccomplished in the construction shown by extending the annular casing11 of the re ceptacle downwardly below the point at which the aperturedsurface is secured to the inner wall of the receptacle 11, as indicatedby 26, and below this downwardly extending portion 26 is suspended anapron 27 which may be supported by the straps 28, in spaced relation tothe lower end of the portion 26.

The size of the opening 29 formed between the portions 26 and 27 of theouter casing may be varied as desired by providing the adjustable sleeve30 adapted to be supported in the desired position of adjustment by thewing nuts 31. A small portion of the materials passing over the inclinedplate 22 may fall through the apertures 25 and these materials may becaught by providing a stocking or the like 32 conveniently formed ofcloth and retained in the position in which it is shown in Fig. 4 by thestrings 33 and 34, the arrangement being such that this stocking may beremoved from time to time to discharge the materials collected therein.

As above stated the suction produced within the classifying receptacleby the exhaust 35, mounted upon the pipe 10, or if desired the pipe 10may lead direct from a dust producing machine or some other source ofsupply.

It may be desirable to direct blasts of air in the form of thin sheetsinto the receptacle 11 at each side of the stream of air entering thepipe 10, and this may be done by providing the auxiliary inlet pipes 36and 37 disposed as best shown in Fig. 6, and air under pressure may besupplied to these auxiliary pipes in the manner more fully disclosed inmy co-pending application, Ser. No. 365,746, filed May 24, 1929. Thesesheets of air as pointed out in the application just mentioned willserve to delay the flow of air towards the exhaust pipe 13 long enoughto give the heavier particles an opportunity to settle out of thewhirling air, as more fully pointed out in said application.

As above pointed out a feature of the present invention of primaryimportance resides in the construction whereby the thin layer of airtraveling adjfint the side walls of the receptacle and the heavymaterials carried by this layer of air are deflected out of thereceptacle, whereupon these heavy particles may be readily removed fromthe small volume of air in which they are suspended. This isaccomplished, in accordance with the present invention, by providing anopening in the side wall of the receptacle 11 through which this thinlayer of air and materials suspended therein is directed into acollecting receptacle or drum 38, and this is accomplished by providingone side of the opening with a knife edge portion 39 which serves todirect the layer of air just mentioned into the receptacle 38 with awhirling movement, as indicated by the arrows in Fig. 6. The heavymaterials which settle in the receptacle 38 will move downwardly intothe collecting hopper 40 at the lower end thereof from which may bedrawn off from time to time or otherwise disposed of. The air whichenters the receptacle 38 may be removed therefrom by an exhaust pipe 41which is shown as communicating with the exhaust pipe 13.

If desired the heavy materials traveling adjacent the side walls of thedome 12 may be removed therefrom in a mannner similar to that justdescribed by providing this dome with the discharge pipe 41 which leadsto a collecting hopper or drum 42 which may be similar to the receptacle38, and air is exhausted from the upper portion of the receptacle 42 bya pipe 43 which leads to the exhaust'pipe 13. The thin sheet of air andheavy particles traveling adjacent the inner wall of the dome 12 will bedirected into the discharge pipe 41 by the knife edge por-v tion 44.

In some constructions it may be desirable to supply air under pressureto the lower face of the apertured surface 22 instead of admitting airfrom the atmosphere to the under face of this surface and in themodified construction shown in Fig. 7 the housing corresponding to theportions 26 and 27 above described is closed to the atmosphere and airis forced into this housing by a fan 45, with the result that anydesired pressure may be produced within the closed housing 46 of thismodified construction to force air upwardly through the aperturedsurface 22.

It will be apparent from the foregoing that the present classifier willseparate the materials being treated into a number of different grades,and in most cases the coarsest particles will be collected in the pipe24. The particles that collect in the lower end of the receptacle 88will be nearly as coarse as those collected in the pipe 24:,while thereceptacle 42 will furnish a somewhat finer grade. The finest materialscollected by this classifier will be delivered by the pipe 19 while thegrades next in size will be supplied by the pipes 20, and 21.

What is claimed is 1. A classifier comprising in combination, an annularreceptacle, means for delivering material laden air into the receptaclewith a whirling movement adapted to effect a centrifugal separation ofthe heavier particles out of the whirling air, means for exhausting airfrom the upper portion of the receptacle, a discharge hopper at thelower end of the receptacle, an annular inclined apertured surfaceextending between the receptacle and hopper to direct the heavierparticles that move downwardly adjacent the wall of the receptacle intothe discharge hopper, and adjustable means for admitting air from theatmosphere to the apertured surface and adapted to regulate the volumeof air that is drawn into the receptacle through the apertured surfaceand materials thereupon.

2. A classifier comprising in combination, a receptacle, means fordelivering material laden air into the receptacle with a whirlingmovement adapted to effect a centrifugal separation of the heavierparticles out of the whirling air, means for exhausting air from theupper portion ofthe receptacle, a discharge hopper at the lower end ofthe receptacle, an inclined apertured surface positioned to direct theheavier particles that move downwardly adjacent the wall of thereceptacle into the discharge hopper and arranged so that air from theatmosphere will pass upwardly through the apertured surface andmaterials thereupon into the receptacle,

and inclined lips adjacent the apertures and arranged to direct the airpassing through the apertures so that it will promote the rotawhirlingair, means for exhausting air from .the upper portion of the receptacle,a discharge hopper at the lower end of the receptacle, an inclinedapertured surface-comprising an annular sheet metal apron positioned todirect the heavier particles that move downwardly adjacent the wall ofthe receptacle intothe discharge hopper and to direct the air jetsupwardly through the particles, a housing arranged to form a closurebelow said apertured surface and provided with an opening for admittingair from the atmosphere to said surface, and adjustable means forregulating the size of said opening.

4. A classifier comprising in combination, an annular receptacle, meansfor delivering material laden air into the receptacle with a whirlingmovement adapted to effect a centrifugal'separation of the heavierparticles out of the air stream, means for removing air from the upperportion of the receptacle, a discharge hopper, at the lower end of thereceptacle, an annular apertured surface positioned between thereceptacle and discharge hopper to direct the heavier materials from theformer into the latter and constructed to direct air upwardly throughthe materials and to impart a rotative whirling movement to the airentering the receptacle through these apertures.

5. A classifier comprising in combination, a receptacle, means fordelivering material laden air into the receptacle with a whirlingmovement adapted to effect a centrifugal se aration of the heavierparticles out of t e whirling air, means for exhausting air from theupper portion of the receptacle, a discharge hopper at thelower end ofthe receptacle, an annular, inclined, apertured surface extendingbetween the receptacle and its hopper to direct the heavier particlesthat move downwardly adjacent the wall of the receptacle into thedischarge hopper, an air chamber below the apertured surface, and meansfor regulating the air admitted to said chamber to thereby control thevolume of air that passes into the receptacle through the aperturedsurface and materials thereupon.

6. An air classifier comprising in combination, a cylindricalclassifying receptacle mounted in an upright position, means forconducting air from the upper portion of the receptacle, a conduit fordelivering material laden air into the receptacle with a whirlingmovement adapted to throw the heavier particles outward by centrifugalforce against the side walls of the receptacle, a cylindrical collectingdrum mounted in an upright position in contacting relation with a sidewall of the receptacle so that the distance between the central axes ofthe drum and rece tacle is less than the sum of the two radii anprovided with an opening between the drum and receptacle and a knifeedge portion at one side of said opening arranged to direct a thin layerof air and the heavier materials traveling adjacent the wall of theclassifier through said opening tangentially into said drum to rotatetherein with suflicient velocit to subject these materials to a secondcentri ugal separation by throwing the heavier particles outwardlyagainst the side walls of the drum to move downwardly therein, and meansfor discharging from the upper end of the drum the air from which thecoarser articles have been removed by centrifugal orce.

In testimony whereof, I have signed my name to this specification.

ALBERT H. STEBBINS.

